The following invention relates to a top and face grinder for a circular saw blade and in particular relates to an indexing mechanism for the saw blade and a stroke position adjustment for a grinding wheel.
Top and face grinders of the top of the type commonly employed in the sawmill industry are sharpening machines for regrinding the top and face portions of the teeth of a circular saw blade. In order to grind each tooth of a circular saw blade, it is necessary to rotate the blade so that the teeth can be ground one at a time. The conventional method of indexing the teeth for each grinding operation is to rotate the saw blade while using an index finger located in the plane of the saw blade which acts as a stop. An arrangement of this type is shown in the context of a side grinding machine in my U.S. Pat. No. 4,823,649. Another example is shown in my copending patent application Ser. No. 07/332,034 "Adjusting Automatic Dual Side Grinder With Quick Retract Cam" filed April 3, 1989 and now U.S. Pat. No. 4,901,604. In these machines as well as in conventional top and face grinding machines, the saw blade is rotated in a direction counter to the direction of cut, but the blade has a slight rotational bias in the opposite direction so that the index finger will drop over the top of an edge of a sawtooth and into the scalloped area underneath the tooth as this rotational bias backs the scalloped portion of the blade against the top of the index finger. This operation is both complex and time consuming because the blade must rotate in two directions to bring each tooth into position for grinding. Additionally, the indexing mechanism must be frequently changed to accommodate saws having different spacings. Also, many saws are of the "skip tooth" variety and cannot be accommodated by conventional indexing mechanisms. Many times the index finger tends to ride too high or too low in the scallop area which consequently requires an adjustment in the position of the grinding wheels. Thus the conventional indexing mechanisms which rely upon fingers aligned in the vertical plane of the blade to catch these scalloped areas beneath the teeth have limited utility and are not versatile enough to accommodate saw blades of different sizes and configurations.
Different sized saws also require an adjustment in the grinding stroke position in order to properly grind each tooth of the blade. For each grinding operation, the grinding wheel must move reciprocally along a grinding stroke axis. The stroke length of the reciprocal motion must be deep enough to pass the grinding wheel across the face or top of the tooth, as the case may be, once for each tooth. With conventional top and face grinders, the operator usually sets the depth of the stroke and uses microswitches to actuate the piston, which carries the grinding wheel, at both the top and bottom of each stroke, Microswitches, however, are wear parts which are prone to failure after a certain number of grinding strokes.